Linear actuator mechanism



March 22, i949. w. P. LEAR LINEAR ACTUATOR MECHANISM Filed Oct. 30. 1945 Patented Mar. 22, 1949 2,464,873 LINEAR ACTUATOR MECHANISM William P. Lear, North Hollywood, Calif., as-

signor,

Illinois l by mesne assignments, to Lear, Incorpo'rated, Grand Rapids, Mich.,

a corporation of Application October 30, 1945, Serial No. 625,496

z claims. (ci. 't4-424.8)

This invention relates to a linear actuator mechanism, and more particularly to such mechanis-m comprising a screw .lack including means whereby no counter torque is applied to the elements of the screw jack when back -pressure is applied thereto.

The invention is particularly applicable o actuators for movable components aboard an aireraf-t. One form of such actuators com-prises a screw jack having a screw rotated by suitable driving mechanism and threadedly engaging a torque tube or sleeve to effect relative extension and retraction thereof. The screw may be fixed against longitudinal movement with respect to a fixed portion of the aircraft, while the outer end of the torque tube or sleeve is connected to a movable member to operate the same; or alternatively, such arrangement of parts may be reversed.

Such screw jacks are generally adjusted ben fore installation to have a predetermined stroke. However, hitherto such adjustment could be eas- -ily upset by rotation of the torque tube when the latter was disconnected from its operated element. Additionally, when in the non-operating condition, the screw jack was subject to rotational counter torque due to back pressure exerted by the movable element. For instance, if the movable element were an air foil control ap of the aircraft, the pressure of the air on the flap on the screw jack would have a tendency to relatively rotate the elements of the screw jack.

It is among the objects of the present invention to provide a linear actuator mechanism including a screw jack, having means preventing any change in its preset adjustment; to provide such a linear actuator mechanism including a screw jack in which back pressure thereon is -prevented from exerting torque on the elements of the screw lack; and to provide a novel, simple, linear actuator mechanism in which the operating stroke may be preset and locked against misadjustment.

These and other objects, advantages and novel features of the present invention will be apparent from the following description and accompanying drawing. In the drawing:

Fig. l is a side elevational view of a linear actuator mechanism incorporating the present invention asl arranged to control the position of a movable control flap of an aircraft.

Fig. 2 is an enlarged longitudinal sectional view through a screw jack forming part of the mechanism shown in Fig. 1. l

Fig. 3 is a transverse sectional view on the line 3-3 oi' Fig. 2.

Fig. 4 is a transverse view, partly in section. on the line 4-4 of Fig. 1.

Referring to the drawing, the linear actuator 2 l mechanism of the invention includes a gear housing. l0 having secured thereto a screw Jack generally indicated at I5. An element of the Ascrew jack, such as the internally threaded torque tube or female threaded member 2li thereof, is se-` cured at its outer end to a crank Ii connected to operate a movable element such as a control flap of an aircraft. A suitable mounting means i2 secures the inner end of the screw jack to a fixed portion of the aircraft. Additionally, a further attachment is provided intermediate the ends of the screw :lack for supporting the same on another fixed portion of the aircraft.

Gear housing I0 comprises a back plate I3, to which mounting means I2 is secured, an intermediate wall portion I4, a spacer plate I6, a locking member I1, and a front wall member I8, all united by suitable means, such as bolts 2| having nuts 22 secured thereto. A worm 23 extends through housing i0, being mounted by suitable bearings therein, and is provided at its outer end with coupling elements, such as 24, which may be secured to mating coupling elements on ilexible shafting for operating worm 23.- The attaching elements for the flexible shafting are secured to plate 26 mounted on housing l0.

Jack screw l5 comprises a threaded shaft or male screw member having a reduced portion 21 extending into housing lll wherein it is mounted in bearings 28 and 3i. A nut 32 secures screw 35 against longitudinal movement relative to housing l0. Torque is transmitted from worm 23 to screw 35 by means of a worm wheel 33 meshing with worm 23 and keyed to reduced portion 21 of a screw 35. l

Screw 35 is enclosed in all positions of jack I5 by means of a protecting housing or dust sleeve 40, having a .length substantially equal to that of the threaded portion of screw 35. Sleeve is maintained in position relative to housing l0 by a collar 4I secured in a suitable manner to sleeve 40 and having a ange 42 engaged beneath a lip 43 on front plate I8 of housing lo. For a purpose to be described hereinafter,

5 the inner end of sleeve 4|! is formed with external splines 43 which engage internal splines 4t formed around the periphery of an annular opening in locking member il. Intermediate its length, sleeve 40 is formed with internal splines 45 which engage external splines 46 on torque tube 20.

Sleeve 40 extends through intermediate mounting means 30, which latter comprises a bearing member 41 having a cylindrical surface 48 engaging sleeve 40 and an outer spherical surface 5I. A pair of clamping plates 52, 53 are provided with spherical flanges 54, 55, respective ly, which engage spherical surface 5I. Clamping plates 52, 53 are arranged to be disposed on either side of a fixed plate of .the aircraft, and .to'clamp such portion between them by means of bolts 58 engaged by nuts 5l. A screw sealing means is provided comprising a flanged packing nut 4Si) threaded on the ou-ter end of tube 40 and containing packing Bl engaging torque tube 20. A locking ring $2 extends around nut 60 and has ends -63 projecting inwardly through an aperture in the nut into engagement in a slot 64 in tube 40.

Torque tube 20 is formed with threads 66 engaging threads 61 of screw 35. At its outer end, tube 20 includes a threaded recess 68 threadedly engaged with the end 1i of a coupling member l2 secured to crank Il. A locking nut 13 retains coupling member l2 and torque tube 20 in predetermined relation. A stop nut 15 is secured on the outer end of screw 35 and retained in position by a locking spring 16, to limit outward movement of torque tube with relation to screw 35.

The operation of the disclosed device is 'as follows. Due to the splined engagement between locking member I1 and dust sleeve 40, the dust sleeve is retained against rotation relatively to housing l0. Splines 45 on dust sleeve 40 en gage splines 46 on torque tube 20. Torque tube 20 is thus retained'against rotation with respect to housing i 0. It will be understood that in linear jackscrew actuators of the character in which the invention is capable of being embodied, the actual travel of the female member 20, and hence the movement of the device actuated by the jackscrew, is limited in both directions by electrical limit switches in the circuit of the motor driving the worm 23, for example as shown in my copending United States application Serial Number 483,515, flied April 17, 1943. Accordingly, the limits of travel of the member 20 may be preadjusted by appropriate settings of such switches. However, notwithstanding such adjustment, it is desired that the relative axial position of the screw and member 20, once established, be maintained during any periods when the actuator is disconnected from the crank il, as for servicing. Thus, by the means of my invention, any inadvertent rotation of the member 20 relative to the screw 35, and occurring while crank Il is disconnected from the actuator, which would have the effect of disturbing the prearrangement thereof is successfully avoided.' Assuming screw 35 stationary, and hence in. proper operating relation with the limit switches, any rotation of member 20 thereabout -could occur only by releasing the connection between sleeve and plate I1. It will have been noted that the latter locking connection is made after the degree of travel of the screw-threaded actuating members 20 and 35 has been established.

In the event torque tube 20 is disconnected, for example from crank H, its preset adjustment cannot be changed by rotation of torque tube 20, as could be done were the described interlocking engagements not provided. Additionally, if back pressure is exerted from the driven load, viz. flap 25, on to torque tube 20, which would ordinarily' tend to rotate the torque tube with respect to screw 35, such rotation is effectively inhibited by the inventive arrangement of torque tube 20 with respect to housing I0, namely, their splined interlocking 45, 46. Thus, an eicient linear actuator mechanism is provided, the adjustment of which cannot be changed after it is mounted in position, and in which back torque cannot effect rotation said sleeve, means carried by said housing for ro. 50'

of the elements of the jack screw. Extension and retraction of the jack screw actuator'is effected through rotation of worm 23 which drives worm wheel 33 rotating screw 35 and operating torque tube 20. The screw 35 is the only member of the jack screw assembly l5 that is rotatable relative to housing I0.

While a specific embodiment of the invention has beensho'wn and described in detail to illustrate the application of the principles thereof, it will be understood that the invention may be otherwise embodied, without departing from such principles.

What is claimed is:

1. A linear actuator comprising, in combination, a housing; a Jack screw mounted in said housing and comprising a screw member. threadedly engaged with an internally threaded tube member, said tube member having external splines; means in said housing effective to rotate said screw member to extend and retract said' tube member; a locking member secured to said housing and having an internally splined aperture; a sleeve having an externally splined end engaged inA said aperture; and internal splines on said sleeve engaging' the splines on said tube member to lock the same against rotation.

2. A linear actuator comprising, in combination, a xed housing, a jackscrew carried by said,

housing and including rotatable male and female threadedly engaged members, one of which is axially movable and the other axially ilxed and rotatable, a sleeve exteriorly of said members, the

axially movable one of said members and said 1 sleeve having mutually interengaging elements for permitting axial movement therebetween and.

to restrain relative rotational movement therebetween, said sleeve and housing having second mutually interengaging elements for restraining said sleeve against rotational movement therebe tween, means for detachably securing said sleevel to said housing whereby said axially movable' member may be rotated about its companion member for linear adjustment of said axially movable member relative to the device actuated by the jackscrew only when said detachably securing means is released, and then only by ro-v tating both said axially movable member and tating said rotatable member and power take-oil means secured to said axially movable member.

WILLIAM P. LEAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENTS Date 

